An ink-jet printer is a type of non-impact printer which forms characters and other images by controllably spraying drops of ink from a print head. The print head ejects ink through multiple nozzles in the form of annular drops which travel across a small air gap and land on a recording media. The drops are very small as ink-jet printers commonly print within a range of 180 to 600 dots per inch (dpi). The ink drops dry shortly thereafter to form in combination the desired printed images.
Ink droplets are ejected from individual nozzles by localized heating. A small heating element is disposed at individual nozzles. An electrical current is passed through the element to heat it up. This causes a tiny volume of ink to be rapidly heated and vaporized by the heating element and ejected through the nozzle. A driver circuit is coupled to individual heating elements to provide the energy pulses and thereby controllably deposit ink drops from associated individual nozzles. Such drivers are responsive to character generators and other image forming circuitry to energize selected nozzles of the print head and thereby form desired images on the recording media.
During printing, ink tends to build up at the nozzle orifices on the print head. This build-up can be caused by excess ink at the orifice that is not vaporized during ejection or ink splatterings that reflect from the recording media. The resident ink on the print head can clog the nozzle orifices and detrimentally disrupt or impair proper printing.
Accordingly, conventional ink-jet printers are equipped with movable wiper assemblies designed to periodically clean the nozzle section of the ink-jet print head to remove any resident ink. The wiper assembly has individual wipers which engage and scrub the orifices on the print head. The wiper assembly is alternately moved to an activated position suitable for cleaning the print head and then to a retracted position where it does not interfere with the print head during printing. As an example, wiper assemblies typically wipe the print head nozzle section once every ten seconds.
This invention concerns proper adjustment of the wiper assembly relative to the print head, and more particularly, to proper initialization of the wiper assembly position. Prior to each wiping operation, the wiper assembly is first moved to a reference position. This reference position is established by a position lever, such as the prior art lever shown in FIGS. 4 and 5, and discussed below in detail. After the wiper assembly reaches its home position, it is then subsequently moved a preset distance to the activated position which allows the wipers to engage the nozzle section.
In prior art ink-jet printers, the reference initialization position for the wiper assembly that is set by the position lever is fixed and cannot be adjusted during manufacturing. A problem arises in that the initializing reference position may end up being inaccurate due to manufacturing tolerances and mechanical imperfections that occur in the production and assembly of an ink-jet printer. If the inaccuracy is severe, the wiper assembly will always initialize to an incorrect reference position which, in some cases, can prevent the wiper assembly from fully or completely cleaning the print head as designed.
Accordingly, it is a goal of this invention to provide a mechanism for establishing the appropriate wiper assembly initializing reference position for a given printer which accounts for any manufacturing tolerances or mechanical imperfections.